I have a Sundowner Sunlite and about 3 years ago I paid to have the ‘trusses’ under the floor replaced. It was a costly repair. (around $1500) That solved the issues. I just had mine in this past week and was told I had many good years left.
It was/is worth it to me to have repaired the issue. I was the 2nd owner and got a good deal on the trailer.